1. Field of the Invention
The present invention relates to a light emitting device, an optical module, and a grating chip.
2. Related Background Art
Light emitting modules are commonly used in order to generate signal light launched into optical fibers constituting optical transmission lines of optical communication systems. The light emitting modules are generally provided with a semiconductor laser device for generating signal light, and an optical system including a lens for guiding the signal light into an optical fiber. The semiconductor laser device applied is a Fabry-Perot semiconductor laser device or a DFB semiconductor laser device. There are also light emitting modules using an external cavity type semiconductor laser system. In the external cavity semiconductor laser system, an optical cavity is comprised of a semiconductor optical element and a Bragg diffraction grating.
Examples of the light emitting devices with the external cavity type semiconductor laser system are described, for example, in Document 1 (“Electronics Letters Jun. 20, 1991 vol. 27 No. 13, pp.1115–1116”), Document 2 (Japanese Patent Application Laid-Open No. 06-5961), and Document 3 (WO94/22187).
Particularly, the light emitting device described in Document 1 is comprised of a grating fiber component and a semiconductor optical element. This grating fiber component has a detachable connector and is coupled through the connector to a package. In this structure of the light emitting device, it is easy to fabricate the light emitting device that generates light of different wavelengths. The first step is to prepare several types of grating fiber components with diffraction gratings of different reflection wavelengths in advance. A grating fiber component of a desired reflection wavelength is selected out of these components and is mounted in the package. This permits the optical module to emit light of the desired wavelength.